Datasheet

 1998-2013 Microchip Technology Inc. DS30289C-page 75

PIC17C7XX

Example 10-2 shows an instruction sequence to initial-

ize PORTB. The Bank Select Register (BSR) must be

selected to Bank 0 for the port to be initialized. The fol-

lowing example uses the MOVLB instruction to load the

BSR register for bank selection.

EXAMPLE 10-2: INITIALIZING PORTB

FIGURE 10-6: BLOCK DIAGRAM OF RB3:RB2 PORT PINS

MOVLB 0 ; Select Bank 0

CLRF PORTB, F ; Init PORTB by clearing

; output data latches

MOVLW 0xCF ; Value used to initialize

; data direction

MOVWF DDRB ; Set RB<3:0> as inputs

; RB<5:4> as outputs

; RB<7:6> as inputs

Note: I/O pins have protection diodes to VDD and VSS.

Data Bus

Weak

Pull-up

Port

Input Latch

Port

Data

Peripheral_enable

Peripheral_output

WR_PORTB (Q4)

WR_DDRB (Q4)

RD_PORTB (Q2)

RD_DDRB (Q2)

RBIF

RBPU

Match Signal

from other

port pins

(PORTA<7>)

Peripheral Data In